Abstract: Since 2004 several studies have been carried out in order to identify the main insectspecies that usually inhabiting the olive ecosystem. The field trials have taken place in two olivegroves, one situated in Olhão and the other one in Loulé, both in Algarve and also underIntegrated Pest Management (IPM). The sampling techniques used differ according to theirpurpose (sticky traps, pheromone traps, pitfall traps and samples of aerial parts of the trees suchas inflorescences, leaves, fruits and branches). Results showed that the main insect pests of olivetree in southern Portugal were the olive fruit fly Bactrocera oleae Gmelin (Diptera: Tephritidae)and the olive moth Prays oleae Bernard (Lepidoptera: Hyponeumetidae). Other insect pests werealso found in our olive groves namely the olive psyllid Euphyllura olivina Costa (Homoptera:Psyllidae), the olive dark beetle Phloeotribus scarabaeoides Bernard (Coleoptera:Curculionidae), the mediterranean black scale Saissetia oleae (Olivier) (Homoptera: Coccidae)and the olive thrip Liothripes oleae Costa (Thysanoptera: Phlaeothripidae). Concerning theauxiliary insects that were found in our olives groves they belong to the following orders andfamilies: Diptera (Syrphidae), Coleoptera (Carabidae, Coccinelidae and Staphylinidae),Hemiptera (Anthocoridae and Miridae), Neuroptera (Chrysopidae) and Hymenoptera(Braconidae, Encyrtidae, Eulophidae, Formicidae and Trichogrammatidae).